1. Field of the Invention
The present invention relates to a door lock control device that can lock and unlock a door by an operation of a drive motor in a heating cooker.
2. Description of the Related Art
A drawer type heating cooker has been proposed in which a drawer, on which an object to be heated can be placed, can be drawn together with an open/close door from a cooker body, and an opening of a heating chamber is closed by the open/close door when the drawer is housed in the heating chamber in the cooker body (Japanese Patent Laid-Open Publication No. 3-45820 (page 2, lower left column, line 6 to page 3, upper right column, line 16, FIGS. 1 to 4, and Japanese Patent Laid-Open Publication No. 11-237053 (paragraphs [0029] to [0032], FIG. 1)). Such a drawer type heating cooker includes an apparatus body (a cooker body) having a cooking chamber (heating chamber) that can house an object to be heated, an open/close door that cuts off the cooking chamber from outside air, and a bottom plate or a heating container (drawer) that interlocks with the open/close door and on which an object to be cooked can be placed. More specifically, the bottom plate or the heating container is smoothly slid by a slide mechanism, and a rotation output of a motor is transmitted to the slide mechanism via conversion means such as a rack and pinion mechanism, thereby allowing the bottom plate or the heating container to be moved in a drawing or housing direction with respect to the apparatus body. In the state where the bottom plate or the heating container is housed in the apparatus body, the open/close door occupies a position for cutting off the cooking chamber from the outside air. In the heating cooker described in Japanese Patent Laid-Open Publication No. 11-237053, a heating container has an opening formed in an upper portion and can be drawn from a cooker body, and the opening is covered with a lid to from a heating chamber for confining microwaves, and a choke groove is provided between an opening peripheral edge of the heating container and the lid to prevent leakage of microwaves.
In a heating cooker such as an electric oven, the inside of the cooker is sometimes cleaned by self-cleaning (burning off inside the cooker) when soiled. The self-cleaning is performed by increasing a temperature inside the cooker and thus performed with a door being locked by a latch device driven by a motor. At this time, the following requirements need to be satisfied for safety. Specifically, it is not allowed that the temperature inside the heating cooker increases to a predetermined temperature (for example, 260° C. or 350° C.) or more until the door is locked. Also, the self-cleaning can be cancelled before the temperature inside the cooker reaches the predetermined temperature, and it is necessary that the door can be immediately unlocked if the door is locked. Further, it is necessary that the door cannot be unlocked until the temperature inside the cooker decreases below the predetermined temperature when the temperature exceeds the predetermined temperature.
In connection to self-cleaning of an electric oven or the like, a door lock device has been proposed in which a lever connected to a motor, a latch lever, and a fixed lever are connected at a locking portion so as to interlock with each other, and a tip of the fixed lever is inserted into a keyhole of a door to lock the door so that the door cannot be opened during the self-cleaning (burning off inside the oven) or when a temperature inside the oven is high (see Japanese Patent Laid-Open Publication No. 3-13730 (page 2, lower left column, line 4 to page 3, upper left column, line 18, FIGS. 1 to 4). Specifically, as shown in FIG. 5, a door 37 is locked by a series of operations such that a motor 22 that is always rotated in a fixed direction rotates a fixed lever 32 interlocking with a motor shaft 23, a tip 35 of the fixed lever 32 is caught in a keyhole 38 formed in the door 37, and the door 37 in which the tip 35 is caught is drawn in a closing direction by a drawing operation of the fixed lever 32. The interlocking structure between the motor shaft 23 and the lever 32 is constituted by a rotating lever 24 mounted to the motor shaft 23, a latch lever 27, and the fixed lever 32, and when the rotating lever 24 is rotated, a locking portion 25 is moved in a movement groove 28, and thus the latch lever 27 is rotated around a locking portion 26, and a movement groove 29 formed in the latch lever 27 engages a locking portion 33 provided in the fixed lever 32 to rotate and draw the fixed lever 32. A groove 34 that the locking portion 33 engages is formed in a mounting plate 21, and a locking portion 31 provided in the mounting plate 21 is locked in a movement groove 36 formed in the fixed lever 32. An actuator 30 attached to the latch lever 27 operates a switch 39, the motor 22 is automatically controlled by the signal from the switch 39 and temperature detection signal from a controller, and stable operations from locking to unlocking the door are performed, thereby preventing a malfunction and reliably closing the door at a high temperature.
A door open/close mechanism of a microwave oven has been also proposed that is configured so that a door is not opened by operating a door opening knob when a cooking switch fails resulting from contact point welding (Japanese Utility Model Publication Laid-Open Publication No. 54-79546 (page 5, line 12 to page 9, line 18). A door hook provided on the door so as to extend into the oven engages a latch hook provided on an oven body to maintain the door in a closed state. A connection lever associated with the door opening knob is connected to a latch lever that operates the latch hook. In the case of the contact point welding of the cooking switch, a structure for preventing rotation of the connection lever is adopted, and thus the latch lever cannot operate the latch hook, thereby preventing the door from opening.
However, for the above described electric oven or the like, if a malfunction of a control device or a failure in a motor driving component occurs, the door is sometimes unlocked though the temperature inside the oven is high, and it is found that such a state causes a dangerous state where a user can open the door.